U.S. Pat. No. 5,692,472 discloses a method and an arrangement for controlling a drive unit. Here, to control the drive unit, the torque or the power of the drive unit is adjusted via an electrical path at least in dependence upon the position of a operator-controlled element actuable by the driver. To monitor this control, a maximum permissible torque or a maximum permissible power is determined on the basis of the position of the operator-controlled element. The actual torque should not exceed the maximum permissible torque and the actual power of the drive unit should not exceed the maximum permissible power. In some applications, for example, in internal combustion engines having gasoline direct injection systems or for diesel engines, it can be provided that this monitoring is only active when the idle state of the drive unit is detected via the position of the accelerator pedal. The idle state of the drive unit is, as a rule, detected in that at least one signal quantity, which represents the position of the actuable operator-controlled element, is compared to a threshold value and a drop below this threshold value represents a released accelerator pedal and therefore the idle state of the drive unit. For these reasons, there are cases of application wherein a reliable idle detection has special significance.
However, this is not always guaranteed only with the comparison to a fixed pregiven threshold value. For example, because of external influences, such as mechanical faults or a foot mat lying on the pedal, idle detection can no longer be possible so that unwanted operating situations are possible via so-called secondary faults in the described application examples.
U.S. Pat. No. 5,229,957 discloses that the mechanical stops of a position transducer, which detects the position of an accelerator pedal, can be learned, that is, can be adapted to changes. This takes place in that the actual end value of the position signal is stored and is substituted by a new position signal value when the actually measured position signal value exceeds or drops below the stored signal position value. In order to prevent that a defectively learned value leads to a continuously defective shift of the position signal, it is provided that, when for a predetermined time at least one of the stored end values is no longer reached, these end values are reset to pregiven start values. On the basis of the at least one stored end value, the actual position signal of the position transducer is determined while considering the measured voltage signal and a pregiven calibration procedure. The actual position signal is then evaluated for controlling the drive unit.